Masamune Date

A mysterious warrior who appears to Hideyoshi and the others several times over the course of the series. She was shown giving Mitsuhide information on the Crimson Armor once. She bears a striking resemblance to Hideyoshi's homeroom teacher, Date-sensei. She is, in fact, Date-sensei. A descendant of the One-Eyed Dragon, Masamune Date, she has taken up the responsibly of avenging her ancestor and returning honor to her family. Her goal was to steal the Crimson Armor, this way, she could use it to unite Japan and bring glory to the Date name. She was visited by a Date clan member from the future, who gave her a device that would allow her to travel to the past.

When she used it, instead of ending up in the Sengoku period in Japan, she wound up in a Japan in an alternate universe. It was because of her, attempting to time travel in the local shrine, that Hideyoshi accidentally ended up in the alternate universe as well.